A downhill ski binding for holding a boot to the ski has releases at both the toe and heel which release the boot from the ski when predetermined forces have been reached. The toe binding releases when the fall or force is to the side. The heel binding releases when the fall or force is toward the front. The toe and heel bindings are at a fixed distance from each other and operate with a stiff downhill boot having a rigid sole. The stiff boot rigidly attached to the ski provides the control necessary for the skier to manipulate the ski. But the rigid attachment between the boot and the ski can cause trouble during a fall when forces are magnified by the leverage of the long ski. And, the chances for the skier getting into trouble are enhanced in downhill skiing by the fast speeds, which increase the forces encountered in falls, and crowded slopes where the skier is surrounded by skiers and snowboarders of varying skill levels, which increase the likelihood of collisions and need for sudden evasive action to avoid collisions. Release bindings are therefore essential to protect the legs of the skier.
In contrast, cross-country skiing is more gentle because the speeds are usually slower, the terrain is usually gently sloping, and there are fewer other skiers in the vicinity. The cross-country boot is not rigidly attached to the ski. It is only attached at the toe allowing the heel to rise off the ski as the skier strides along. The boot is flexible and usually has a sole with three holes across the toe which couple to three pins on the ski. This arrangement is flexible and provides some protection for the skier during a fall. Instead of the ski being rigidly attached to the boot as on a downhill ski, the heel of the boot can move away from the ski during a fall thereby substantially lessening the chances for injury to the leg.
A similar arrangement is found on a telemark ski which is similar to a cross-country ski but is also useful on downhill slopes. The telemark ski is shorter for a given skier than a cross-country ski making it easier to turn. Because the skier requires a given surface area to support his weight, the telemark ski is slightly wider than the cross-country ski to compensate for the decrease in length. The binding and boot arrangement of the telemark ski are similar to the cross-country ski with the three pin system being common.
Even though cross-country and telemark skis may be considered safer than downhill skis, injuries still occur. The increasing use of plastic boots instead of leather boots has helped reduce the injury rate somewhat. Some releasable bindings have become available but they are not widely used. An improved releasable binding for cross-country and telemark skiers would therefore be of value.
A release ski binding for downhill and cross-country skis is shown in U.S. Pat. No. 3,877,712 utilizing torsion bars on each side of the boot to control levers engaging the heel of the boot. The entire ski binding assembly rotates up around the toe when the skier desires to raise the heel for cross-country use.
U.S. Pat. No. 4,348,036 shows a safety binding for nordic skis which features a cylindrical structure mounted across the front of a boot having cupped rotation surfaces at each end. A releasable binding is mounted on the ski having two arms each with a ball member on the end facing the cupped rotation surfaces on the ski. The boot rotates up and down around its toe on the ball members. When unusual forces are encountered, a spring which holds the arms in place allows them to spread apart thereby releasing the ball members from the ends of the cylinder on the boot.
A similar arrangement is seen in U.S. Pat. No. 4,621,828 which shows a safety binding for nordic skis. Instead of moving arms, a rigid bracket is mounted on the ski having the cupped rotation members. A cylinder mounted transverse to the toe of the boot has a spring which pushes out two ball ends into the cupped rotation members. As in U.S. Pat. No. 4,348,036, the boot rotates up and down around its toe on the ball members. When unusual forces are encountered, the ball ends push in against the spring releasing the boot from the ski.
U.S. Pat. No. 5,518,264 discloses a free heel/anterior release binding utilizing a cable. A rocker means at the heel of the boot rotates under sufficient stress to cause the effective lengthening of the cable relative to the length of the boot allowing the boot to slip free.
The most widely used telemark release bindings commercially available are the CRB 3-pin cable and the CRB classic cable models available from Voile of Salt Lake City, Utah. Both feature a release plate on which either the 3-pin cable or classic cable mounts are attached. The boot is secured in either of these arrangements around the heel by a cable. The mount and release plate remain with the boot. The rear of the release plate features a semicircular indentation which abuts a semicircular friction pad that is permanently attached to the ski. The front of the release plate has a shallow ball type socket perpendicular to the bottom of the release plate and facing toward the front of the ski. Mounted on the ski in front of the ball type socket is a spring in a barrel having a ball end facing the ball socket. The skier engages the ski by placing the rear of the release plate against the friction pad on the ski and then pushing the toe down against the barrel forcing the ball end into the barrel until the ball end engages the ball type socket. When unusual backward forces are encountered, the release plate pushes the ball end against the spring releasing the binding. Unusual forward forces do not insure release in this release mechanism because the release plate remains engaged with the semicircular friction pad.